Field of the Invention
The invention relates to a structure capable of resisting electromagnetic signals for electronic devices, wires and components, e.g. electromagnetic interference shielding film used in printed circuit board, and in particular to a structure capable of resisting electromagnetic signal for flexible electronic substrate.
Brief Description of the Related Art
Currently, the technologies of electronic industries are dedicated to developing electronic devices which are lighter, thinner and smaller. Printed circuit boards are required materials in electronic devices, and are becoming thinner, and smaller with high voltages resistance. Accordingly, electromagnetic signal interference has become a major issue as electronic devices become lighter, thinner and smaller.
Generally, the problem with electromagnetic signal interference may be resolved by circuit layout design, e.g. a signal transmitting layer in combination with a grounding layer may be used for a complicated circuit layout so as to reduce the electromagnetic signal interference. Alternatively, electromagnetic interference shielding material may be applied on the circuit layout of a flexible printed circuit board to restrain the electromagnetic signal interference.
One of the known commercial available electromagnetic interference shielding material is a conductive adhesive film with a single or multi-layered conductive metallic film containing silver, copper or nickel on the surface by sputtering or chemical deposition. The conductive metallic film can enhance shielding effect of the conductive adhesive film against the electromagnetic signal interference. The conductive metallic film comprises a B-stage polymer having cured cross-linking reaction and conductive particles.
In addition, electronic or electrical devices, especially those running with high power, are inevitably confronted with the problem of thermal dissipation. The traditional method to solve this problem is to use additional means or devices to dissipate heat occurred therefrom, for example, a mandatory air convection system consisted of one or more fans. However, for those small or micro electronic elements such as a CPU, which are used in compressed spaces such as, mounted on a printed circuit board, ifs far from enough to use said mandatory air convection system to solve the heat dissipation problem because there are not enough space for heat dissipation.
A related art disclosed an electromagnetic interference repressor using a composite magnetic body with high thermal conductivity. As shown in FIG. 1, the electromagnetic interference repressor 10 comprises two composite magnetic body 1,1 and a conductive support 4 interposed between the two composite magnetic body 1,1. The conductive support 4 may be the textiles of a conductive fiber. The composite magnetic body 1 contains the organic binder 2 and the soft magnetic powder 3, wherein the organic binder 2 may be polyethylene resin or polyester resin; and the soft magnetic powder 3 may be Fe—Al—Si alloy or Fe—Ni alloy. The composite magnetic body 1 can suppress the electromagnetic interference by complex permeability of the soft magnetic powder 3 in high frequency absorption. However, the organic binder 2 used for forming the composite magnetic body 1 may be deformed and deteriorated due to thermal effect. Moreover, the poor thermal conductivity of the organic binder 2 may hinder the heat dissipation of electronic components. The electromagnetic interference repressor 10 cannot simultaneously solve the problems of the electromagnetic interference and the heat dissipation of electronic components.